Thread forming mechanism



6 3 Sheets-Sheet 1 F. NELL THREAD FORMING MECHANISM Filed June 16, 193

Oct. 4, 1938.

Oct. 4, 1938. F. NELL 2,131,965

THREAD FORMING MECHANISM Filed June 16, 1956 3 Sheets-Sheet 2 Oct. 4, 1938. NELL 2,131,965

THREAD FORMING MECHANISM Filed June 16, 1956 3 Sheets-Sheet 3 H il B W M M W I My W11;.QIQMJ WWW Patented Oct. 4, 1938 UNITED STATES PATENT OFFICE 2,131,965 THREAD FORMING MECHANISM Application June 16, 1936, Serial No. 85,563

18 Claims.

This invention relates to thread-forming mechanism, and especially to taps of the type designed to cut tapered threads and to collapse at the end of each thread-cutting operation.

5 The present application is in part a continuation of the subject matter of my co-pending ap- 'plication, Serial No. 5,129, filed February 5, 1935.

Throughout this specification the term chaser is used in its broad as well as its limited sense. That is, it may mean the actual cutting tool and its carrier or holder, or the definition may be confined to the cutting element alone.

It is a primary object of the present invention to devise a thread-cutting machine having a series of slidable chasers detachably connected with a cam element, in association with means for accurately positioning all of the chasers simultaneously so that during assembly a single movement of the cam element will readily and assuredly pick up all of the chasers for interconnection therewith. More specifically, the present invention contemplates carrying out the preceding object where the cam element is centrally disposed and designed, upon axial movement, to positively move the chasers radially in both directions.

It is another major object of this invention to provide new and improved means for adjusting a chaser-controlling cam element relative to its operating means. In this connection it is an object to provide an adjustment feature which permits the removal of the chasers for sharpening without in any way dismantling the machine proper.

It is another important object of the present invention to devise a thread-cuttingmachine having a set of removable chasers which may be replaced accurately without disturbing the, original setting of the machine and therefore with- 40 out requiring trial cuts to place the machine in condition to cut the same size threads.

It is a further object of my invention to devise a thread-cutting machine comprising a main body and a detachable head designed to carry chasers, with a chaser-positioning cam that is fully retractible to permit very quick chaser removal and immediate substitution of heads of different sizes.

A further object of the present invention resides in the provision of improved means for collapsing the chasers of the thread-cutting machine, and especially to devise improved collapsing means for a tap which embodies a positively controlled receding action for cutting tapered threads. I

It is another object of this invention to improve upon tapered thread-cutting mechanism of the typedisclosed in the Newman Patent No. 1,811,802, in such manner as to facilitate the return of the chaser-controlling cam to cutting 5 position after it has been operated to collapse the chasers. I

It is a further major object of the present invention to devise -improved adjustable means for selecting the. desired length of thread to be cut. 10 This object contemplates, both individually and in combination, a major adjustment of the thread length and a minor or limited adjustment of the thread length. r Still another major object is to provide, in a .15

collapsible thread-cutting machine, cushioning means for preventing shock or damage upon axial movement of the chaser controlling means, and especially, to devise an improved cushioning means that becomes eiiectivewhen the control cam is shifted in a direction to place the chasers in thread-cutting position.

It is a further and related important object of the present invention to provide a combined cush- ,ioning'means and an adjustable stop for yieldingly resisting the movement of the parts and checking them during their return to operative or thread-cutting position.

The foregoing and further objects of themesent inventionwill clearly appear upon a consideration of the following detailed description when taken in conjunction with the accompanying drawings wherein:

Figure 1 represents a longitudinal section taken vertically through a collapsible tap comprising a preferred form of the present invention. In this view the manually operable lever that stands vertically is-shifted 90' out of its true position for convenience of illustration. This and the remaining parts are so disposed as to extend thechasers to thread-cutting position.

Figure 2 is an end view of the tap of Figure 1, showing the face of the head which carries the chasers;

Figure 3 is a face view of a chaser comprising a cutter and the slidable holder upon which it is mounted. thev cutter being shown in the form that it takes after being sharpened a number of times;

Figure 4 is fragmentary sectional view taken substantially on the plane indicated by the line" 4-4 in Figure 2;

Figure 5 is a sectional View similar to Figure 1 but showing the parts in the position that they assume when the chasers are collapsed; m

' head l6, and at their inner V Figure 6 is a fragmentary sectional view through only the tap body and a portion of the mechanism which surrounds the same, taken substantially on the line 65 in Figure 2;

Figure 7 is a view corresponding to Figure 6 but showing the mechanism surrounding the body in a position corresponding to the collapsed position of the chasers;

Figure 8 is a fragmentary sectional view'taken longitudinally of only the body of the device and a surrounding cushioning and stop means, as. seen when looking substantially upon the plane of line 8-3 in Figure 2. In this view the parts surrounding the body are so disposed as to correspond with thread-cutting position of the chasers;

Figure 9 is a view similar to Figure 8 showing the mechanism surrounding the body in the position that it assumes upon collapse of the chasers;

Figure 10 represents an enlarged fragmentary sectional view taken through the check valve assembly in one end of the pistonof Figures 8 and 9; V

Figure 11 is a fragmentary section corresponding to the left-hand ends of Figures 1 and 5 but with the chaser-controlling cam so adjusted as to be completely retracted to permit ready removal of the chasers; and I Figure 12 is an enlarged sectional view' similar to Figure 11 but showing a slightly modified type of cam-adjusting means.

The improvements and additions illustrated in the drawings and about to be described are disclosed in association with collapsible taps of the type shown in Newman and my co-pending application Serial No. 5,129, aforementioned; and although these are desirable forms it will be appreciated that my improvements and additions may be used on many other thread forming machines within the knowledge of those skilled in the'art and within the scope of the appended claims.

With further reference to the drawings wherein like numerals are employed to designate like parts and'with particular reference for the moment to Figures 1 and 2, the foundation or the main body structure of the preferred embodiment of this invention comprises an elongated hollow body l5 to which is secured a chaser carrying head I6 by means of detachable studs I'I. At one end the body has an integral tail stock I8, and at the other end the head l6 carries a plurality of cutting elements inthe form of circular chasers l9 secured to radially slidable chaser holders 20. The holders 20 are insertable through and radially slidable within a corresponding series of slots 22 in the front face of ends are provided with fingers 23 which form with thebodies of the holders a series of cam slots 23a. The head I6 is hollow and shaped internally to 'slidably but non-rotatably receive a tapered chaser-controlling cam member 24, which has on its periphery a set of integral fingers or wings 26 that cooperate with the cam body to provide a series of cam grooves 25. The fingers 23 of the chaser holders are received within the cam grooves 25 of the cam member, and the wings 26 of the cam member are received in the cam grooves 23aof the chaser holders. Therefore, as the cam member is moved forwardly or to the left in Figure 1,

the chaser holders will be positively cammed radially outwardly; and Vice versa, as the cam member is moved rearwardly, the chaser holdthreaded end of a coupling rod 28.

Patent 1,811,802

ers will be positively drawn radially inwardly.

The cam member 24 has a rearward cylindrical extension 21 which rather snugly fits the bores of the body and head of the machine to guide the cam member and lend support to the latter dur- 5 ing threading operation, and the cam member is internally threaded to receive the externally As will be seen later the cam member is axially*adjust able relative to this rod and may be locked with 10 respect thereto in any desired position of adjustment. The rearward end of the rod 28 is peripherally grooved and detachably coupled to an integral forked forward extension 29 of a plunger 30. The plunger 33 is disposed within the bore 15 of the body 15 and is designed for reciprocation therein.

The plunger 30 has a central slot 32 formed transversely therethrough, .and to the opposite walls of said slot are secured shoes 33. These 20 shoes are slightly inclined from the vertical plunger .and'its shoes 33. All of this and some of the further structure yet to be described is more fully disclosed in NewmanPatent No. 1,811,802, and therefore only sufficient descrip- 3 tion and explanationwill be here given to pro.- vide a general understanding of the arrangement and mode of operation of the old parts of the illustrated' machine.

It will be perceived that any downward move- 2 ment of the bar 35 will cause the grooves 34 to exert a camming action on the shoes 33 to force the shoes 33, and with them theplunger 30, rearwardly. After a predetermined downward movement of the bar, it will come to a position where its horizontal platforms 3!, which open rearwardly from the grooves 34, are brought into horizontal alignment with horizontal bottom faces 38 on the shoes 33. At this moment as shown in Figure 5, shoes 33 are permitted to ride rearwardly over the faces 38 and thus permit the plunger 30 to be retracted further rearwardly at any desired speed as they are no longer under control of the cam grooves 34 of the vertical bar 35.

The purpose of the mechanism just described is to first impart a gradual receding motion to the chaser-controlling cam 24 to thus cut a tapered internal thread within a piece of work, (such, for example, as a valve housing or pipe m which rotates relative to the tap), and thereafter upon completion of the taperedthread to permit spring means (yet to be described) to quickly shift the plunger 30 rearwardly and collapse the chasers. The mechanism for causing vertical downward movement of the bar 35 gradually to produce a tapered thread is as follows.

Theupper end of the bar 35 has an integral cam element 39' in the form of a shoe which is slidably. received in a cam groove 43 of an inclined longitudinally arranged bar 42. At its rear end the bar 42 is fastened at 43 (and may be fastened at 43a to obtain a different degree collar 45 that is slidably mounted on the'tap body I5. At its forward end the bar42 is pivoted at 46 to the control collar 45. Upon moving the control collar 45 with its attached bar 42 rearwardly, the inclined groove will cause the coacting shoe-39 to move downwardly along the groove and thus vertically shift the bar 35 downwardly. 1

Rearward movement of the collar is brought about by interconnecting it with the piece of work being threaded so that as the cutters enter the piece of work the latter will push the collar 45 axially of the tap in a direction away from the work. This interconnecting mechanism is as follows:

The control collar 45 has a series of integral radially extending eyes 47 through which freely pass a corresponding series of threaded rods 48. Nuts 49 are threaded upon the rods 48 so that upon relative adjustment of the eyes 41 with respect to the rods 48 the adjustment may be maintained by locking the nuts against the eyes 41 (see also Figure 4). 1

The forward ends of the rods 48 are secured to a corresponding set of links 50 which in turn are rigidly secured to a set of forwardly extending pins 52 that are threaded into and locked with respect to a work engaging ring 53. The ring 53 surrounds the tap head adjacent the chasers and is peripherally grooved to receive a channeled oil ring 54 provided with a socket 55 adapting it for the reception of a pipe (not shown) that supplies a cutting lubricant. The lubricant passes to the several chasers individually through small ports 5! under pressure from the channel of ring 54. As the ring 53 is in abutting contact with the work, it is moved gradually rearwardly relative to the tap body upon relative rotation of the work and the tap; or, otherwise stated, the tap body gradually moves forwardly in accordance with the pitch of the thread being cut because its cutting elements l9 are entering the piece of work, with the result that the control collar 45 is forced rearwardly. Preferably the work is rotated in fixed axial position and the tap, while non-rotatable, is positively advanced in well known manner by means of a lead screw. I

At the rear end of the body l5 there is disposed a manually operable lever 56 which is projected into the body and pivoted thereto at 57 and which has a camming toe 58 slidably engageable with the forward end wall of a slot 59 formed in the body of the plunger 30. Upon rocking this lever the plunger may be shoved forwardly in a manner later to be explained in detail, and it will be appreciated that various other arrangements known in the art may be utilized for this purpose.

At the extreme rear end of the body {5 there is provided a transverse pin 60 which passes through the plunger 30 and which is movable forwardly and rearwardly in a longitudinal through-slot 62 formed in the body l5. The extremities of the pin 60 are received in a collapsing and expanding ring 53 that is mounted for reciprocation on the body l5. In a manner now to be set forth the springs previously referred to are designed to shove the collapsing ring 63 rearwardly upon completion of a full tapered thread, thus acting through the pin 60, plunger 3!] and the chasercontrolling cam 24 to quickly withdraw the chasers inwardly away from the completed thread and thus permit the piece of work to be removed easily and without damage to the threads.

With reference now to Figures-6 and 7, the control collar 45 has a segmental portion thereof housing a'spring assembly. comprising a small cylindrical shell 64, which at its closed endis constantly in'abutment withthe collapsing ring 63 and which contains a long relatively light spring 65 extending forwardly into contact with the forward end of the control collar 45. A pin 65 is secured to the collar 45 and projects into the spring 65 a sufficient distance to insure that the latterv will be maintained in proper position. Spring 65, for a purpose later to be explained, is always under some compression with a tendency to urge the control collar 45 and the collapsing J ring 53in opposite directions.

A second and heavier spring 68 is disposed within a cylindrical bore 67. of the control collar. This spring reacts against the forward end of the control collar and is normally held in either neutral or but very' slightly compressed position by a threading operation. However, as rearward movement of the collar 45 is brought about in the manner before explained, the long spring 65 immediately begins to be further compressed and, when the rear end of the sleeve 69 comes into contact with the collapsing ring 63 the heavier spring 68 begins to become compressed. This spring compression occurs because the ring 63 cannot move rearwardly until the plunger 30 is released by the vertical bar 35. This release isi' 85 timed to first permit adequate spring compression-that is, the bar surfaces 38 reach the level of the shoe surfaces 31 at a point where the desired spring compression is obtained. Thereafter, upon releaseof the shoes 33 the springs areiifio permitted to react and kick the collapsing ring 53 rearwardly, thus withdrawing the chaser-operating cam to the position illustrated in Figure 5.

At this time the spring assembly will be in the position illustrated in Figure '7. {.45

"At or just after the release of shoes 33 from the bar grooves,'the control ring 45 engages the collapsing ring so that the shoes and the plunger 35 I Will be carried rearwardly in positive manner at i the same rate as the collar (instead of at the much-e50 slower rate of the time interval prior to shoe release), if for any reason the springs should fail to kick the collapsing ring rearwardly.

After the withdrawal of the chaser-operating cam to the position illustrated in Figure 5, therear55 is a spring tendency to urge collar 45 forwardly; but this cannot be done without raising the bar 35 vertically, and'such' vertical movement is prevented because the bar surfaces 38 will be pressed against the lower shoe surfaces 31 to lock the-1; bar 35 against vertical movement and in this way lock the collar 45 against forward movement. It therefore becomes necessary to start the forward or return movement by manually operating the lever 56 to force the plunger 30 forwardly until its-2.65 shoes 33 laterally enter the bar grooves 34 and permit upward travel of the bar 35.

' Due to the inclination of the grooves 34, it would 'be difficult to use the lever 55 alone to complete the return or forward movement of the plunger;:

70 To eliminate this difficulty the elongated spring 65 serves a still further function by reacting directly against the collar 45 to urge it forwardly and thus lift the bar 35 vertically. The spring 65 thus serves the triple function of (11 augmenting s has been cut and spring 94, carried by a the kicking action of the spring 68, (2) assuring a locking action of the mechanism in collapsed position regardless of the length of the thread that (3) facilitating the completion of a return movement of the mechanism to thread-cutting position.

Preferably, another spring assembly, constructed, mounted, and arranged exactly like that just described, will be disposed at a diametrically opposite locus in the control ring for purpose of balance and smooth action.

Reference will now be had to Figures 8 and 9, wherein there is disclosed a major adjustment for thread length, and a device for cushioning the shiftable mechanism upon its return to threadcutting position. As seen in these views the control collar 45 has a segmental portion shaped to receive between it and the body I5 a number of cooperating parts. This shaping includes the provision of a longitudinal through-slot 13 within the collar for reception of a rack bar 14 which is slidable in the guideway or slot 13 and which has a number of teeth forming interdental spaces 15 facing radially outward toward the collar. Fitting into any one of these spaces is a tongue '16 formed on a plate 11 which is detachably secured to the forward end of the collar 45 by a cap screw 18. In this way the rack bar may be adjusted forwardly or rearwardly and locked in any one of a number of positions corresponding to the number of interdental spaces for a purpose later to be explained.

The rack bar has a longitudinal slot 19 into which projects a pin 89 formed as part of a threaded element 82 that is screwed into the collar. Slot [9 also receives a pin 83 formed on a square element 84 that is set into a small piston 85 which reciprocates longitudinally in a barrel or cylinder 86 that is longitudinally arranged and attached to the tap body l5. Therefore, during rearward travel of the collar 45 the pin will engage the pin 83 and move the piston rearwardly in its cylinder. During this movement air is admitted to the working chamber of the piston cylinder by way of a longitudinal passage 81 in the piston, a passage 88 through the square element 84, and a check valve assembly 89 at the forward end of the piston. Some air may also enter the chamber through a port 90 in the'forward end of the cylinder but the cross-sectional area of this port is such that it alone would not permit the free and rapid retraction of the piston. The purpose of the port 90 is to retard the return stroke of the piston when the check valve assembly 89 is "closed.

Closing movement of the piston is effected by a lug 9| at the rear end of the rack bar which engages, the element 84 after a predetermined forward movement of the collar 45.

As seen in Figure 10, the check valve assembly may comprise a hollow sleeve 92 in communication with the passage 81 and affording a seat-fora ball valve 93 that is pressed toward said seat by a hollow plug 95 that is screwed into the forward end of the piston.

' Pulling the piston rearwardly causes the valve to unseat and admit air freely to the working'chamber of the cylinder; Upon movement'in' the opposite direction, however, the valve will seat and the'only escape for air is through the small port 90, as a result of which the return or forward movement of collar 45 is cushioned. Various equivalent porting means may be utilized For example, port 99 may be eliminated and the valve seat provided with one or more small grooves .justment and for locking which will permit a slow escape of the air rearwardly into the passage 81 shoved forwardly by the manually operable lever When the forward end of the piston comes into r abutment with the end wall of the cylinder, forward motion of the collar 45 is stopped and at this time the position of the collar 45 will of course depend upon the position of the stop' lug 9i of the rack barrelative to the collar 45.

of any one of the interdental spaces 15 for engagement by the finger "I6 as previously pointed out to determine the thread length. Variation of the thread length follows from the fact that this;

justable feature, however, is provided primarily;

to set the work-engaging structure in such position that a receding action will start simultaneously with the thread-cutting operation.

With particular reference now to Figures 1 and 11, as aforestated the chaser-controlling cam" member 24 is adjustable longitudinally of the threaded rod 28. The means for effecting this adthe parts in adjusted position are as follows. The'forward end of the rod 28 is tapped to receive an externally threaded;- sleeve 96 which extends, slidably through the front end of the cam member 24 and which is provided with a head 91, that can be rotated by an actuating tool. The threaded portion of sleeve98 has a transverse slot therethrough which, receives a pair of diametrically opposed brake shoes 98 that are slidable radially in the slot and that may be forced outwardly into locking enwhen the collar 45 is' This relative position is predetermined through selectionv adjacent interdental gagement with diametrically opposite portions "of the tapped bore of rod 28'by rearward motion. of a tapered stem 99-that fits between the shoes and forms an integral part of a manually adjustable screw I99. Screw I89 is threaded into the sleeve 95 and may be manuallyoperated by inserting a tool through the hollow head 91 of the,

sleeve 96.

To effect an adjustment, screw I09 is loosened to unlock the brake shoes 98 and the sleeve 96 is rotated within the rod 28 to obtain the desired relative disposition of each part, after which the, screw 199 is again locked to expand the brake shoes 98; For preventing-rotation of the rod 23 during this adjustment and for preventing undesired rotation of the rod at any other time relative to cam member 24-, a yielding latch mecha-v nism is provided comprising. aplug I92 longi tudinally slidable in the front end of the plunger 30, but locked against rotation with respect thereto by a pin I 93. A spring 194 urges the plug forwardly, and complemental latching serrations I 05 are provided on the plug and on the rear end of the rod 28. 'This latching mechanism is substantially identical with that shown in Newman Patent No. 1,912,298.

The'adjustment just described accurately determines the thread diameter because it definitely locates the head 91 longitudinally of the device, and the head 91 in turn definitely locates the cam member 24, for in actual working positions as illustrated inFigures 1 and 5 the forward end ment of the latter.

of the cam member is always tightly in contact with the rear end of the head 91. This contact is obtained, not through rotation of the cam member which can only slide in the head I6, but through bodily rotating as a unit all of the screw-threaded elements which are housed within the cam member 24. Upontightening the screw IE9 to lock the brake shoes 98, the manipulation of the head 91' with the proper tool will cause the sleeve 96, the screw I and the rod 28 to rotate as a unit within the cam member to advance or retract the latter depending upon the direction of rotation of the head 9'7. This manual operation is permitted by the yielding latch mechanism I02 to I which, however, has sufficient resistance to rotation to prevent any inadvertent bodily rotation of the screw-threaded elements to get the cam member out ofadjustment. I

In Figure ll the cam member 24 is shown sufiiciently retracted, by the adjustment just described, to take the cam fingers or wings 26 out of overlapping engagement with the complemental fingers 23 of the chaser holders, thus permitting the chasers to be readily withdrawn radially for sharpening, adjustment or repair. A chaser is shown partly removed in Figure 11, and in Figure 3 there is shown a removed chaser having its cutting element resharpened. Due to the fact that removed and replacement of the chasers does not involve any alteration of the position of the head 91 longitudinally relative to the plunger 38, the chasers may be replaced and the screw-threaded elements bodily rotated to bring the cam 24 into engagement with the rear end of. the head 91, thus assuredly bringing the parts exactly in the same position that they previously had prior to removal of the chasers. Hence, operation of the machine may be resumed to cut threads of exactly the same size, and this is important because it eliminates any trial and error adjustments and trial cuts with attendant loss of time and possible slight inaccuracies.

A highly important feature of this invention resides in the provision of means for facilitating a quick coupling between the cam members and the chaser holders upon insertion or replace- As seen in Figure 2 the body of the cam member 24 has a plurality of fiat inclined faces corresponding in number to the number of chasers. The inclined faces terminate in forward extensions or ledges I06, as best seen for example in Figure 11, which project forwardly a slight distance beyond the forward extremities of the cam wings 23. Therefore, when the chasers are replaced the holders can be simply pressed radiallyv inwardly until their cam fingers 23 engage ledges I65 in which position every one of the cam fingers 23 is accurately located for reception by a corresponding groove 25 of the cam, and as the adjustment is performed to move the cam member forwardly all of the chaser holders are picked up and intercoupled, simultaneously and without difiiculty, to the cam member. This feature is shown but not claimed in myv aforementioned co-pending application Serial No. 5,129, the claims which are directed to cam member adjusting and locking means of the character above set forth.

Figure 12 is carried forward from said co-pending application and discloses a tap head which differs from the head of the form already described chiefly in the provision of a slightly modified form of cam adjusting and locking means. In this modified form a sleeve 28a is provided which differs in no material respects from sleeve 28, and this sleeve receives an adjusting sleeve 26a having a head 91a differing only from the corresponding elements of the form already described in the elimination of the locking shoes 98. In place of the locking shoes and the screw I00, there is provided a screw-threaded element I01 having a manually operable head I08. To look all of the screw-threaded elements together for bodily rotation, the head I08 is rotated until the rear end of the screw I 9'! is jammed into abutment with. the internal end surface I 09 of the rod 28a. Ledges I 06 are provided in Figure 12 for facilitating the replacement and intercoupling of the chasers as already set forth.

In both forms the head I6 is readily removable from body I5. Although the cam member 24 is firmly supported radially in the head I6, it can readily slide out of the same rearwardly. Access to the studs I1 is had by performing the adjustments above described to remove the chasers, and thereafter, upon removal of the studs I! the head I6 can be replaced by a'larger or smaller head which also fits the body I5 but which is designed for use in cutting another range of thread, diameters.

The particular means for mounting and adjusting the cutting elements with respect to their holders forms no part of the present invention, but is fully set forth and claimed in my co-pending application Serial No. 23,901, filed May 28, 1935.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A tap for cutting tapered threads comprising a body structure carrying chasers, a chasercontrolling device movable axially of the body structure, an external control member slidable on said body structure longitudinally thereof, a transverse bar operating through said device and provided with a shoe, said external control member having a longitudinally arranged inclined cam groove complemental to said shoe, and adjustable stop means for predetermining the point along said groove at which said shoe is ing arrangement for said working chamber designed to permit free relative movement of the control member in a rearward direction while resisting rapid forward movement thereof.

3. In the combination defined in claim 2, one of said devices being longitudinally adjustable to govern the thread length.

. external member, whereby the der determine the maximum extent of continued forward movement, and means associated with said piston and cylinder to produce a cushioning action during said continued forward movement.

5. A collapsible tap comprising a body provided with slidable chasers, a device mounted for axial reciprocation in said body to position said chasers, a control member and a collapsing member mounted in spaced relation on said body and movable relatively toward each other in response to thread-cutting action, the control member being operatively associated with said device and the collapsing member being connected to said device, a spring engaged by one of said members and designed to engage the other only after a predeterminedamount of relative travel between said members, and means for causing said spring to separate said members after it has been deformed a predetermined amount through continued relative travel of said members toward each other.

6. In the combination defined in claim 5, said spring being a relatively heavy coil type spring,

and there being a lighter but longer coil spring concentrically arranged with respect to the first mentioned spring and having its ends constantly in engagement with the control and collapsing members respectively.

' '7. In a thread-cutting machine, a body member carrying chasers, control means movable longitudinally of saidbody member in opposite directions to extend or retract said chasers, an operating device for said control means also movable longitudinally of said body member, interconnecting means between said control means and said device adapted to be released at a predetermined point in the movement of said control means in chaser retracting direction, an adjustable stop between said device and said body member to limit relative movement thereof in one direction, said adjustable stop including a cushioning device, a spring mechanism comprising a plurality of springs interposed between said control means and said device operable to rapidly move said control means in chaser retracting direction upon release of said interconnecting means, means to move said control means in chaser extending direction and against said stop, said spring mechanism being arranged so that the plurality of springs assists in the initial portion, and one spring assists in the final portion, of said last named movement.

.8. In a thread-cutting machine, a body mem ber carrying chasers, control means for said chasers, a longitudinally movable operating device releasably interconnected with said control means, an adjustable stop and cushioning device arranged between said operating device and said body member, spring means interposed between said control member and said device comprising two spring elements, said spring elementsbeing adapted to move said control means in chaser retracting direction upon release of said operating device and to assist in the initial return movement thereof towards chaser extending position, and one of said springs being continuously operable thereby assisting in the final portion of said return movement of said device against said adjustable stop and cushioning device.

9. In a thread-cutting machine, a body member carrying extensible and retractable chasers, operating means for said chasers including a longitudinally movable member associated with said body member and a control member releasably connected therewith, stop means for limiting movement of said movable member in chaser extending direction, said stop means being adjustable and provided device, spring mechanism interposed between said movable member and said control member comprising a plurality of spring elements operable upon release of said control member to move the same in chaser retracting direction, means to return said movable member to chaser extending position against said stop means, said spring mechanismbeing arranged so that only a single spring element is operative during the final portion of said return movement.

10. The combination set forth in claim '7 wherein said cushioning device comprises a piston and cylinder associated with said body member and said adjustable stop.

11. The combination set forth in claim I wherein said spring mechanism comprises a light spring and a heavy spring coaxially arranged within said operating device, a tubular plunger element associated with each of said springs adapted to successively engage said control member when said device is moved in chaser retracting direction.

12. In a thread-forming machine; a Su port, an abutment on said support, a plurality of radially movable chasers carried by said support; means for controlling the radial positions of said chasers, comprising a member movable axially of said support; work engagingv means adjustably mounted on said member; and stop means adjustable longitudinally of said member and engageable with said abutment on said support for limiting axial movement of said member in a forward direction. v

13. In a thread-forming machine, a support; a plurality of radially movable chasers carried by said support; means for controlling the radial positions of saidchasers, comprising an axially movable member; and work engaging means on said member; said work engaging means being formed to receive a cooling medium and to direct the same against said chasers.

'14. In a thread-cutting machine, a support; a chaser controlling means mounted for axial movement along said support; a work engaging element carried by said means and adjustable longitudinally thereof; a cushioning device carried by said support; and an abutment on said.

controlling means adjustable longitudinally thereof and adapted to engage said cushioning device and limit movement of said controlling means in a forward direction.

15. In a thread-cutting machine, a body member, a control member shiftable longitudinally of said body member, a cylinder mounted on said body member, a piston in said cylinder, a lateral projection on said piston, an abutment means fixed to said collar, a second abutment means adjustably secured to said collar, said first abutment means being arranged to engage said projection and withdraw said piston from said cylinder when said control member is shifted in one direction, said second abutment being arranged to engage said projection and move said piston into said cylinder when said control member is shifted in the opposite direction, means associated with said piston and cylinder forming a porting arrangement for permitting free flow of air into said cylinder when said piston is withdrawn and a slow flow of air out of said cylinder when said piston is moved into said cylinder, whereby movement of said control member, in said first named direction is cushioned.

16. In a thread-cutting machine, the combination set forth in claim 15, wherein said second named abutment comprises a slotted bar member adjustably secured to said control member with said first named abutment and said piston projection received in said slot.

17. In a thread-cutting machine, the combination set forth in claim 4, wherein the device detachably secured to said external member comprises a bar member having external rack teeth thereon and provided with an abutment portion, together with means cooperating with said rack teeth to hold said bar in any one of several positions on said external member.

18. In a thread-forming machine, a support; a plurality of chasers radially movable in said support; means for controlling the radial positions of said chasers during thread-forming operation, comprising an axially movable member; and stop means adjustable longitudinally of said movable member and adapted to engage with means on said support to limit movement of said member in a forward direction, said adjustable stop means including a bar arranged for adjustment longitudinally of said movable member and having a series of recesses, and a device secured to the movable member and projectable into any selected one of said recesses to lock the bar against longitudinal movement relative to said movable means.

FREDERIC NELL. 

